Fire and smoke alarm device

ABSTRACT

A fire and smoke alarm device which is activated by the presence of smoke and/or excessive heat. The device includes a housing having an air sampling chamber and means therein to induce the flow of air therethrough. A fire sensing means is provided in the air sampling chamber which will activate an alarm circuit when the temperature in the chamber reaches a predetermined level. A sealed and insulated temperature controlled compartment is also provided in the housing and has a photoelectric cell therein which will activate an alarm circuit upon the cell sensing a predetermined light intensity in the air sampling chamber. The air sampling chamber has a light source mounted therein which illuminates a portion of the chamber. A clear lens is positioned between the air sampling chamber and the compartment for admitting light into the compartment so that the photoelectric cell can sense the light intensity in the air sampling chamber. Means is provided for maintaining the temperature in the compartment at 120* F. so that the photoelectric cell will function with the required sensitivity.

United States Patent Jensen 1 Apr. 25, 1972 [54] FIRE AND SMOKE ALARMDEVICE [72] Inventor: John L. Jensen, Estherville, Iowa [73] Assignee:Jensen Industries, Inc., Des Moines, Iowa [22] Filed: Apr. 15, 1970 [21]Appl.No.: 28,865

Primary E.taminerJohn W. Caldwell Assistant E.taminerDaniel MyerAttorney-Zarley, McKee & Thomte l 5 ABSTRACT A fire and smoke alarmdevice which is activated by the presence of smoke and/or excessiveheat. The device includes a housing having an air sampling chamber andmeans therein to induce the flow of air therethrough. A fire sensingmeans is provided in the air sampling chamber which will activate analarm circuit when the temperature in the chamber reaches apredetermined level. A sealed and insulated temperature controlledcompartment is also provided in the housing and has a photoelectric celltherein which will activate an alarm circuit upon the cell sensing apredetermined light intensity in the air sampling chamber. The airsampling chamber has a light source mounted therein which illuminates aportion of the chamber. A clear lens is positioned between the airsampling chamber and the compartment for admitting light into thecompartment so that the photoelectric cell can sense the light intensityin the air sampling chamber. Means is provided for maintaining thetemperature in the compartment at 120 F. so that the photoelectric cellwill function with the required sensitivity.

5 Claims, 5 Drawing Figures PATENTEDAPR 25 m2 FIRE AND SMOKE ALARMDEVICE The smoke and fire alarm of this invention is an improvement overapplicant's earlier device which was disclosed in US. Pat. No.3,447,152, which issued on May 27, 1969. Ap-

plicants earlier device functioned quite satisfactorily but thesensitivity range of the sensing elements therein varied somewhat as thecomponents were subjected to varying temperatures. In order for a deviceof this type to receive Underwriters Laboratorys certification, it mustfunction within a prescribed sensitivity range.

Therefore, it is the principal object of this invention to provide acombined fire and smoke alarm which is activated by the presence ofsmoke and/or excessive heat.

A further object of this invention is to provide a combined fire andsmoke alarm which functions within the prescribed sensitivity range.

A further object of this invention is to provide a fire and smoke alarmincluding an air sampling chamber and means therein to induce the flowof air therethrough so that the air is properly sampled.

A further object of this invention is to provide a fire and smoke alarmhaving a temperature controlled compartment therein which houses aphotoelectric cell, and other temperature effected components.

A further object of this invention is to provide a fire and smoke alarmwhich is electrical and which may be powered by an ordinary householdwiring circuit.

A further object of this invention is to provide a fire and smoke alarmwhich is economical to manufacture, durable in use, efficient inoperation and refined in appearance.

These and other objects will be apparent to those skilled in the art.

This invention consists in the construction, arrangements andcombination of the various parts of the device, whereby the objectscontemplated are attained as hereinafter more fully set forth,specifically pointed out in the claims, and illustrated in theaccompanying drawings in which:

FIG. 1 is a perspective view of the device of this invention mounted ona wall surface.

FIG. 2 is a sectional view of the device with portions thereof cut awayto more fully illustrate the invention.

FIG.'3 is an enlarged sectional view as seen'along line 3 of FIG. 2.

FIG. 4 is an enlarged sectional view as seen along line 4-4 of FIG. 2.

FIG. 5 is a schematic drawing of the electrical circuity of thisinvention.

The numeral generally designates the device of this invention comprisinga housing 12 in which the operating components of the device of thisinvention may be fully housed and, for example, may be composed ofmetal, certain plastics, etc. Housing 12 is provided with a back 14,front 16, top 18, bottom 20, and opposite sides 22 and 24. Housing 12 isprovided with an opening 26 in its bottom which communicates with an airsampling chamber generally designated by the reference numeral 28. Airsampling chamber 28 includes a vertically disposed chamber portion 30which is in communication with opening 26, and inclined chamber portion32 which extends upwardly and laterally from chamber portion 30,vertically disposed chamber portion 34 extending upwardly from the upperend of chamber portion 32, and chamber portion 36 which is incommunication with the upper end of chamber portion 34 and opening 38formed inside 22. Air sampling chamber 28 is provided with screens 40and 42 which prevent bugs or the like from entering the chamber butwhich permit the flow of air therethrough.

The numeral 44 refers to a heat sensing switch mounted in chamberportion 32 which is adapted to activate an alarm circuit upon thetemperature in chamber 28 reaching a predetermined level. The numeral 46refers generally to a heat resistor positioned in chamber portion 34.Heat resistor 46 heats the air in the chamber portion 34 to createconvection currents therein which pulls the air through the opening 26,chamber portion 30, chamber portion 32, chamber portion 34,

chamber portion 36 and outwardly through opening 38. A light source 48having a focusing lens 48A thereon is mounted in the upper end ofchamber portion 32 and is adapted to direct light downwardly therefromas indicated by the arrow in FIG. 2. The numeral 50 refers to a piece ofreflective material which is provided in the chamber portion 32 asillustrated in FIGS. 2 and 4.

Housing 12 also includes a sealed temperature controlled compartment oroven 52 having an insulating material extending therearound which isgenerally designated by the reference numeral 54. Compartment 52includes a tubular portion 56 which extends between chamber portion 32and the interior of compartment 52 as illustrated in FIGS. 2 and 4. Alens 58 is mounted in tubular portion 56 and is designed to permit lightto pass therethrough into the interior of compartment 52. Lens 58 keepsdust off of cell 60 and seals the compartment 52. Cell 60 is aphotoelectric cell mounted at the inner end of tubular portion 56 incompartment 52 adapted to sense the light intensity passing through lens58. Cell 60 is maintained in position by the heat conductive metalbracket 62 extending thereover as illustrated in FIG. 3. Bracket 62maintains cell 60 in proper position as well as serving as a heatconductor. Bracket 62 is secured to a heat conductive bracket 64 whichsupports a heating element 66 thereon as illustrated in FIG. 3. Heatingelement 66 is controlled by an adjustable thermostat 68 positioned inthe compartment 52 so as to maintain the temperature within thecompartments 52 at 120 F. plus or minus llfipercent. The brackets 64 and62 conduct heat from the heating element 66 to the photoelectric cell 60so as to insure that the photoelectric cell will be maintained at theproper precise operating temperature.

In FIG. 2, the numeral 70 refers to the main or primary audio signal orhorn with the numeral 72 referring to the trouble audio signal or horn.In FIG. 2, the numeral 74 refers to a transformer with the numerals 76and 78 identifying capacitors. Numeral 80 refers to an adjustablepotentiometer which is also illustrated in FIG. 2. A switch 82 isprovided in bottom 20 of the housing and is movable from test to resetpositrons.

The wiring circuitry of the device is illustrated in FIG. 5 and merelyshows the circuitry which permits the device to function. The circuitrydoes not form an essential part of this invention and for that reasonwill not be described in detail. The heart of the invention of thisdevice is the structure and method by which the compartment 52 ismaintained at degrees so that the photoelectric cell 60 and othertemperature effected components will function within the prescribedsensitivity range.

In operation, the device is plugged into any ordinary household circuit.The circuitry of FIG. 5 includes a trouble circuit which causes theordinary household current to activate the horn 72 if the lamp 48 shouldfail. In order for a device of this type to receive UnderwritersLaboratorys certification, a trouble circuit for the lamp 48 is requiredwith a trouble circuit for power failure being an optional feature.

The operation of the device causes the heat resistor 46 to createconvection currents in the air sampling chamber 28 so that the air willbe drawn through the chamber 28 and properly sampled. If the temperaturein chamber portion 32 rises above a predetermined level, the heat switch44 causes the horn 70 to be activated thereby signalling that adangerous condition exists. If smoke exists in the area around thedevice 10, it will be drawn into the air sampling chamber 28 asindicated by the arrows. In the absence of smoke in chamber portion 32,a certain amount of light passes through the lens 58 with thephotoelectric cell 60 sensing that light intensity without activatingthe alarm circuit. If approximately 10 per cent or less black smoke isintroduced into chamber portion 32 or if 4 percent or less light smokeis introduced into chamber portion 32, the light intensity thereinincreases so that a greater light intensity passes through the lens 58thereby activating the photoelectric cell 60 which in turn activates thealarm circuit so as to activate horn 70. By precisely controlling thetemperature within compartment 52, it is possible to achieve theprescribed range of sensitivity necessary to obtain certification of thedevice. The device of this invention functions within a tolerance of 2percent smoke obscurity at 70 F., and this sensitivity will not varyover a plus or minus 50 percent at either 32 F. or 120 F. Thus, thetolerance factor at 32 F. or 120 F. must be between 1% percent and 3%percent. The fact that the temperature within the compartment 52- ismaintained at the 120 temperature and the fact that means is providedfor conducting heat to the photoelectric cell 60 insures that the propersensitivity range will be achieved.

It should be noted that the electrical circuit of FIG. 5 includes twovoltage regulators (4.7 volts and volts) to achieve 50 percent plus orminus sensitivity.

Thus it can be seen that a unique tire and smoke alarm has been providedwhich senses heat and smoke within a proper sensitivity range. Thesensitivity is achieved by the sealed and temperature controlledcompartment 52 together with the means for insuring that convectioncurrents will be created in the chamber 28 so that the air is properlysampled. Therefore it can be seen that the device accomplishes at leastall of its stated objectives.

lclaim:

l. A heat and smoke alarm device, comprising,

a housing having an air sampling chamber provided therein,

means for inducing the flow of air through said air sampling chamber,

a heat sensing means in said air sampling chamber connected to an alarmcircuit adapted to activate the same when the temperature in said airsampling chamber rises to a predetermined level,

a light means in said air sampling chamber,

said housing having a temperature controlled compartment formed therein,

said compartment being sealed from said chamber,

a photoelectric cell in said compartment connected to an alarm circuitadapted to activate the same when smoke intensity in said air samplingchamber reaches a predetermined level,

means for controlling the temperature in said compartment wherein saidsmoke sensing means will be maintained a predetermined operatingtemperature,

and a lens between said compartment and said chamber for permitting thepassage of light therethrough so that said photoelectric cell can sensethe smoke intensity in said air sampling chamber.

2. The device of claim 1 wherein said compartment has a thermostaticallycontrolled heating element therein adapted to maintain the temperaturein said compartment at a predetermined temperature.

3. The device of claim 2 wherein a heat conductive bracket meansconnects said heating element and said photoelectric cell so that heatis conducted to said cell to maintain said cell at a predeterminedtemperature.

4. The device of claim 2 wherein said predetermined temperature is F.

5. The device of claim 3 wherein said bracket means maintains saidphotoelectric cell in position adjacent said lens.

1. A heat and smoke alarm device, comprising, a housing having an airsampling chamber provided therein, means for inducing the flow of airthrough said air sampling chamber, a heat sensing means in said airsampling chamber connected to an alarm circuit adapted to activate thesame when the temperature in said air sampling chamber rises to apredetermined level, a light means in said air sampling chamber, saidhousing having a temperature controlled compartment formed therein, saidcompartment being sealed from said chamber, a photoelectric cell in saidcompartment connected to an alarm circuit adapted to activate the samewhen smoke intensity in said air sampling chamber reaches apredetermined level, means for controlling the temperature in saidcompartment wherein said smoke sensing means will be maintained apredetermined operating temperature, and a lens between said compartmentand said chamber for permitting the passage of light therethrough sothat said photoelectric cell can sense the smoke intensity in said airsampling chamber.
 2. The device of claim 1 wherein said compartment hasa thermostatically controlled heating element therein adapted tomaintain the temperature in said compartment at a predeterminedtemperature.
 3. The device of claim 2 wherein a heat conductive bracketmeans connects said heating element and said photoelectric cell so thatheat is conducted to said cell to maintain said cell at a predeterminedtemperature.
 4. The device of claim 2 wherein said predeterminedtemperature is 120* F.
 5. The device of claim 3 wherein said bracketmeans maintains said photoelectric cell in position adjacent said lens.